1. Field of the Invention
The present invention relates to an ultrasound diagnosis apparatus for use in the field of medical treatment, and more particularly to setting of a plurality of sub arrays on an array transducer.
2. Description of Related Art
Ultrasound diagnosis apparatuses are used in the field of medical treatment for the purpose of diagnosing diseases of a living body (patient). More specifically, ultrasonic diagnosis apparatuses transmit an ultrasonic pulse to a living body and receive a reflected wave therefrom for forming an ultrasonic image based on a receiving signal obtained by the reflected wave received.
A two-dimensional (2D) array transducer (or transducer array) is used for effecting two-dimensional scanning of ultrasonic beams to thereby form a three-dimensional echo data acquiring space within a living body. A 2D transducer is generally composed of a plurality of transducer elements arranged along X and Y directions.
In some 2D array transducers, a plurality of sub arrays are defined on the 2D array transducer for the purpose of channel reduction of a transmission/reception section, simultaneous formation of a plurality of receiving beams, or other purposes. Conventionally, a plurality of sub arrays are fixedly defined on the 2D array transducer. For example, a plurality of sub arrays having a rectangular shape are set with respect to a 2D array transducer, and in this case, the shape of each sub array cannot be changed. Japanese Patent Laid-Open Publication No. 2001-276064 discloses the grouping of a plurality of transducer elements in which the structure of each group is fixed. Japanese Patent Laid-Open Publication No. 2001-104303 discloses a structure for performing phase adjustment and summation (or beam formation) in two stages. Japanese Patent Laid-Open Publication No. Hei 9-322896 discloses, in FIG. 6, that a plurality of groups are fixedly set for a 2D array transducer, that a plurality of first beam formers are connected to the plurality of groups, and that a plurality of second beam formers are provided at the subsequent stage of the plurality of first beam formers. U.S. Pat. No. 5,832,923 discloses that a plurality of 2D sub arrays are defined on a 2D array transducer and that a plurality of groups are defined on each sub array. None of these documents, however, describes dynamically changing the shape of each sub array.
When the structure or form of the sub array is fixedly defined, a problem results in that a beam profile preferable to specific transmitting and receiving wave conditions cannot be obtained. For example, there may be a tendency for side lobes to be generated in a specific beam scanning direction.